1. Field of the Invention
The present invention relates to the technology fields of liquid crystal display, and in particular to a thin film transistor, the manufacturing method thereof, a thin film transistor array substrate and a liquid crystal panel.
2. The Related Arts
Thin flat panel display with small body and low power consumption is widely used. The existing thin flat panel display comprises liquid crystal display (LCD) and organic electroluminesence display (OLED).
Liquid crystal display (LCD) is consisted of color or monochrome pixels with a certain amount, which is placed in front of the light source or the reflector. Liquid crystal display has low power consumption, high image quality, small size, and light weight, so it is favored to become the mainstream of display.
Organic electroluminesence display is different from the liquid crystal display. It doesn't need backlight. It is consisted of an organic coating layer and a glass substrate. When current passes through, the organic materials will emit light. Organic electroluminesence display has the characteristics of self-luminous, high brightness, wide viewing angle, high contrast, flexible, low-power consumption, which receives widespread attention.
The thin film transistor (TFT) is usually used to drive the thin flat panel display, which realizes display screen information with high speed, high brightness, and high-contrast. Recently, metal oxide thin film transistor has several advantages of high mobility, good transparency, stable film structure, low production temperature and low cost, which receives more and more attention. Especially in the metal oxide TFT technology represented by indium gallium zinc oxide (In—Ga—Zn—O, IGZO), it can achieve higher resolution comparing with a-Si TFT and have high yields, low costs and energy conservation comparing with low temperature poly-silicon (LTPS) TFT. In summary, IGZO TFT technology has superior overall performance, which has a lot of breakthrough progress.
Referring to FIG. 1, the top-gate top-contact structure of the exiting IZGO TFT mainly comprises an IGZO layer 230, a gate insulating layer 240, a gate electrode 250, a passivation layer 260, a source electrode 270 and a drain electrode 280 formed on a substrate 210. Wherein, the IGZO layer 230 is an N-type semiconductor deposited on the substrate as a conducting channel. The source electrode 270 is a metal conductor deposited on the substrate 210 and coupled with one side of the IGZO layer 230, which is used to receive the source driving signal. The drain electrode 280 is a metal conductor deposited on the substrate 210 and coupled with the other side of the IGZO layer 230, which is used to receive the drain driving signal. The gate insulating layer 240 is an insulating layer deposited on the substrate 210, the IGZO layer 230, the source electrode 270, and the drain electrode 280, which is used to insulate the IGZO layer 230, the source electrode 270, and the drain electrode 280. The gate electrode 250 is a metal conductor deposited on the gate insulating layer 240, which is used to receive the gate driving signal. The passivation layer 260 is an insulating layer deposited on the gate insulating layer 240 and the gate electrode 250, which is used to protect the units. However, when the external light irradiate on the thin film transistor mentioned above, the light will affect the threshold voltage of the TFT, and the changes of the threshold voltage accompanying with bias stress will be accelerated, which will result in the display chaos of flat panel display. At the same time, the mobility of the semiconductor will be changed, which affects the resolution of the flat panel display. Moreover, the work function difference between the using metal of IGZO and that of the source electrode 270 and the drain electrode 280 is larger, so it results in larger contact resistance between the IGZO layer and the source electrode 270 and the drain electrode 280, which affects the output efficiency.